The present invention relates to a non-contact inspection system for detection and identification of defects on the edges of sheets of glass, especially the edges of flat automotive glass. The system is intended to operate on a continuous production line at line speed, and to be used for detection and identification of a wide variety of types of defects, including chips, cracks, poor grinding and other edge defects.
In processes for manufacture of glass in sheet form, it is necessary to be able to inspect the sheets of glass for defects. Such defects may be in the form of scratches, bubbles, chips, blemishes and a wide variety of other defects. In addition, the manufacturer of the sheet glass needs to know whether the defects are insignificant e.g. minor in nature and thus acceptable to the customer, or significant such that the sheet of glass would not conform to specifications established by the customer. It is important to able to conduct the inspection on-line in the production process, at production speeds, so that defects may be rapidly identified and communicated to production personnel and/or the sheets of glass with the defects may be readily and quickly separated from sheets of glass meeting quality specifications in an effective manner.
Methods have been developed for the inspection of sheets of glass using optical techniques. Apparatus and a method that are particularly intended for use in inspection of sheets of glass in a production line, at production speeds, in a manner that shows the magnitude, type and location of the defects in the sheets of glass are disclosed in Canadian Patent Application No. 2252308 of Adam Weiss and Alexandre Obotnine filed Oct. 30, 1998. Such apparatus and method, referred to herein as viewing area apparatus, are especially intended to be an integral part of a glass processing system.
The aforementioned Canadian Patent Application No. 2252308 is directed to a method for the inspection of sheets of glass, in which the sheets of glass are transported through the beams of lasers. Such an inspection is intended to detect bubbles and other defects in the sheets of glass but not defects on the edges of the sheets of glass except to the extent that those defects extend from the edges of the sheets of glass into the sheets of glass. The lasers are not in a position to inspect the edges of the sheets of glass.
Detection of defects on the edges of the sheets of glass is also important, as such defects may affect both visual and physical properties of the sheets of glass.
Apparatus and a method have now been found for inspection of the edges of sheets of glass in a production line, at production speeds, especially in a manner that shows the magnitude, type and location of the defects.
Accordingly, one aspect of the present invention provides an inspection system for the edge of a sheet of glass, comprising:
a) means to support and move a sheet of glass in a plane in a first direction, said means to support and move the sheet of glass maintaining the glass in a constant plane;
b) a laser that provides a beam of laser light;
c) an optical recording device for said laser beam;
d) means to direct the laser beam onto said edge of the sheet of glass at an angle to said first direction and to direct light reflected therefrom to said optical recording device, the light reflected from the edge of the sheet being coaxial with light directed onto the edge of the sheet; and
e) means to control the total path length of said laser beam from said laser to said edge and from said edge to said optical recording device at a substantially constant length.
In preferred embodiments of the apparatus of the present invention, the system additionally comprises software that utilizes information from the light detection system to determine the location, type and magnitude of defects in the edges of the sheet of glass.
In a further embodiment, the system additionally has means to record the location, type and magnitude of defects in the edges of the sheets of glass, optionally including a display or a defect map, especially a defect map displayed on a screen.
Another aspect of the present invention provides a method for the inspection of the edge of a sheet of glass, comprising:
a) supporting and moving a sheet of glass in a plane in a first direction, said sheet of glass being maintained in a constant plane;
b) directing a laser beam onto said edge of the sheet of glass at an angle to said first direction and directing light reflected therefrom to an optical recording device, the light reflected from the edge of the sheet being coaxial with light directed onto the edge of the sheet; and
e) controlling the total path length of said laser beam from said laser to said edge and from said edge to said optical recording device at a substantially constant length.